CN109923378B

CN109923378B - Method for producing a sensor element of a thermal flowmeter, sensor element and flowmeter

Info

Publication number: CN109923378B
Application number: CN201780067588.4A
Authority: CN
Inventors: 斯特凡·加布苏埃尔; 亚历山大·格林; 汉诺·舒尔特海斯; 托比亚斯·波尔; 马丁·巴特; 阿纳斯塔西奥斯·巴达利斯; 拉尔斯·奈尔林; 马丁·阿诺尔德; 奥利弗·波普
Original assignee: Endress and Hauser Flowtec AG
Current assignee: Endress and Hauser Flowtec AG
Priority date: 2016-11-04
Filing date: 2017-10-10
Publication date: 2021-08-17
Anticipated expiration: 2037-10-10
Also published as: US20200191629A1; EP3535549B1; DE102016121110A1; US11054293B2; CN109923378A; EP3535549A1; WO2018082873A1

Abstract

The invention relates to a method for producing a probe (10) of a thermal flowmeter for measuring the mass flow of a medium in a measuring tube, comprising the following steps: introducing a probe core (13) in the form of a material to be melted into a first probe sleeve (11), the first probe sleeve (11) having an open first end (21) and a closed second end (22) remote from the first end (21); melting the probe core (13); quenching the probe core (13) to a temperature below the curing temperature; a thermocouple (31) is attached to the contact surface (14) of the cured probe core (13). The invention also relates to a probe obtained according to the production method and to a flow meter comprising a probe according to the invention.

Description

Method for producing a sensor element of a thermal flowmeter, sensor element and flowmeter

Technical Field

The present invention relates to: a method for producing a probe for a thermal flow meter for measuring the mass flow of a medium in a measuring tube, a probe and a flow meter.

Background

Thermal flow meters have been the prior art for a long time; one or more probes are introduced into the medium flowing through the measuring tube, wherein the probes are designed to measure the temperature of the medium or to heat the medium. For example, the temperature measurement probe may be positioned downstream of the heating probe such that the temperature measurement probe is heated by a medium heated by the heating probe.

For high measurement accuracy of thermal flow meters and for low measurement accuracy fluctuations between different flow meters of the same type, a constant manufacturing quality of the used probe is important. Important for the high sensitivity of the probe in relation to the high mass flow of the medium is the low thermal resistance between the contact surface of the probe with the medium and the heating or temperature measuring thermocouple.

The prior art, for example, DE102008015359a1, shows a probe with a probe sleeve having a thermocouple embedded in a filler material.

A disadvantage of this solution is that the filler material, in terms of heat transfer between the probe and the medium surrounding the probe, on the one hand causes fluctuations between a series of different probes and, on the other hand, is liable to age the probe, so that with increasing time of use, such a probe must be recalibrated to avoid measurement errors.

Disclosure of Invention

It is therefore an object of the present invention to propose a probe having improved stability in terms of its production and long-term performance.

This object is achieved by a method for producing a probe for a thermal flow meter according to the invention, by a probe for a thermal flow meter according to the invention and by a thermal flow meter according to the invention.

The method according to the invention for producing a probe of a thermal flowmeter for measuring the mass flow of a medium in a measuring tube has the following steps:

introducing a probe core in the form of a material to be melted into a first probe sleeve, wherein the first probe sleeve has an open first end and a closed second end distal from the first end;

melting the probe core;

quenching the probe core to a temperature below the solidification temperature;

a thermocouple is attached to the contact surface of the cured probe core.

By melting and subsequently quenching the probe core at the probe core-probe sleeve contact surface, a connection layer is created in which the probe core is firmly connected to the probe sleeve, which ensures good heat transfer and long-term stability in terms of thermal properties of the probe.

In one embodiment of the method, the contact area is prepared by machining for attaching a thermocouple.

In one embodiment of the method, after quenching the probe core, the probe core is exposed in the first region by partially removing a barrel wall of the first probe sleeve.

In one embodiment of the method, after the exposing, a second probe sleeve having an open third end and an open fourth end is bonded, in particular welded, in a sealing manner to the first end through the open third end, wherein the second probe sleeve is completely wrapped around the first region.

In one embodiment of the method, a first one of the sub-regions is machined such that the sub-region of the probe core is spaced apart from all surfaces of the first or second probe sleeve, wherein the sub-region includes all of the first cross-sections of the probe core that intersect or contact the contact surface.

In one embodiment of the method, the thermocouple is attached to the contact surface of the probe core by a solder layer or a sintered layer.

The probe according to the invention of a thermal flowmeter for measuring the mass flow of a medium in a measuring tube, produced by the method according to the invention, comprises:

a first probe sleeve having an open first end and a closed second end;

a probe core at least partially filling a first probe sleeve;

a thermocouple thermally coupled to a probe core, wherein the thermocouple is configured to increase or detect a temperature of the probe core;

wherein producing the probe core includes melting a material to be melted in the first probe sleeve.

In one embodiment of the probe, the probe core has a first longitudinal axis, an outer surface connected to the first probe sleeve, a centroid, and a contact surface facing away from the second end of the probe core relative to the centroid, wherein the thermocouple is attached to the contact surface by a solder layer or a sintered layer.

In one embodiment of the probe, the probe core includes a first region protruding in an axial direction from the first probe sleeve, wherein the first region has a contact surface.

In one embodiment of the probe, the first region is surrounded by a second probe sleeve having an open third end and an open fourth end, which second probe sleeve is bonded, in a sealing manner, in particular welded, to the open first end of the first probe sleeve via the third end, wherein the first region of the sub-regions is processed such that the sub-regions of the probe core are spaced apart from all surfaces of the first or second probe sleeve, wherein the second region comprises all first cross sections of the probe core which intersect with or contain the contact surface.

In one embodiment of the probe, the first probe sleeve and/or the second probe sleeve are cylindrical.

In one embodiment of the probe, the first probe sleeve comprises stainless steel, wherein the probe core has a thermal conductivity greater than 100W/(m × K), wherein the probe core has at least one metal from the following list: copper, silver, aluminum, nickel, indium, gold, tin. In the case of the use of a probe as heating element, the significantly better thermal conductivity of the probe core compared to stainless steel achieves a uniform temperature distribution at the heat transfer surface between the probe and the medium flowing around the probe.

In contrast, in the case of using the probe as a temperature sensor, rapid temperature adaptation of the probe core to temperature changes of the medium and uniform temperature distribution at the contact surface between the probe core and the thermocouple are achieved.

The thermal flow meter for measuring a mass flow of a medium according to the present invention comprises:

a measurement tube having a second longitudinal axis;

at least one probe according to the invention embedded in the measuring tube;

electronic operating circuitry configured to operate the at least one probe.

In one embodiment of the probe, the thermal flow meter comprises at least two probes, wherein the electronic operating circuitry is configured to heat at least one first probe, wherein the electronic operating circuitry is configured to determine the temperature of the medium by at least one second probe.

Drawings

The invention will now be described with reference to exemplary embodiments.

Figure 1 shows a schematic process for manufacturing a probe according to the invention.

Fig. 2a) to 2d) show the steps of producing a probe according to the invention.

Fig. 3 shows an enlarged and distorted view of the manufacturing stage shown in fig. 2 d).

Fig. 4 shows an embodiment of a probe according to the invention.

Fig. 5 shows a schematic front view of a thermal flow meter with two probes according to the invention.

Detailed Description

Fig. 1 shows an embodiment of a method sequence 100 for producing a probe 10 according to the invention.

In a first step 101, a probe core 13 in the form of a material to be melted is introduced into a first probe sleeve 11, wherein the material to be melted has copper or silver, and wherein the first probe sleeve 11 is made of stainless steel.

In a second step 102, the probe core 13 is melted so that the liquid material of the probe core 13 collects in the region of the closed second end 22 of the first probe sleeve 11. When the probe core 13 is a fluid, an intermetallic joint layer in which the material of the probe core 13 and the material of the first probe sleeve 11 are mixed is formed at the interface between the probe core 13 and the first probe sleeve 11.

In a third step 103, the probe core 13 is quenched to a temperature below its solidification temperature. Due to the formation of the intermetallic connection layer, contact between the probe core 13 and the first probe sleeve 11 is maintained after the probe core is cured.

In a fourth step 104, the probe core 13 is exposed in the first area by partially removing the barrel wall of the first probe barrel 11.

In a fifth step 105, the contact surface 14 for attaching the thermocouple 31 is prepared by machining, in particular smoothing and aligning processes, which can be achieved, for example, by drilling or milling.

In a sixth step 106, the thermocouple is attached to the contact surface by means of a solder layer or a sintered layer.

In a seventh step 107, a second probe sleeve 12 having an open third end 23 and an open fourth end 24 is attached, in particular welded, to the first end 21 in a sealed manner through the open third end, wherein the second probe sleeve 12 is completely wrapped around the first region.

Advantageously, the first region is machined in sub-regions such that the sub-region 16 of the probe core is spaced apart from all surfaces of the first probe sleeve 11 and/or the second probe sleeve 12, wherein the sub-region 16 comprises all first cross-sections of the probe core which intersect or contact the contact surface 14.

Fig. 2 shows a cross-section of a probe 10 according to the invention in various stages of manufacture.

Fig. 2a) shows a cross section of the probe 10 in a stage in which the first probe sleeve 11 has a probe core 13 in a fluid or cured state.

Fig. 2b) shows a cross-section of the probe at a stage of exposure of the probe core in the first region, wherein the exposure of the probe core allows radial access to the probe core 13 with respect to the first longitudinal axis 15.

Fig. 2c) shows a cross-section of the probe in a stage of attaching the thermocouple 31 to the contact surface 14 of the probe core 13 after the probe core 13 is exposed in the area.

Fig. 2d) shows a cross section of the finished probe 10 with the second probe sleeve 12, the second probe sleeve 12 being attached, in particular welded, to the first end 21 of the first probe sleeve 11 via the third end 23.

Fig. 3 shows an enlarged view of a section of the finished probe 10 shown in fig. 2d), wherein the view is distorted horizontally so that minor details can be seen. The thermocouple 31 is attached to the contact surface 14 of the probe core 13 via a solder layer or sintered layer 32. The probe core 13 is supported on the side opposite the contact surface 14 by a support 33, wherein the support 33 is an extension of the first probe sleeve 11. Embodiments of probe 10 without support 33 are also contemplated. The probe core 13 is thus configured in the subregion 16 such that the probe core 13 is spaced apart from all surfaces of the second probe sleeve 12. If the probe does not include the support 33, the probe core 13 in the subregion 16 is spaced from all surfaces of the first and

second probe sleeves

11, 12. The spacing of the probe core in the sub-region from the second probe sleeve or from the first probe sleeve and the second probe sleeve ensures a uniform temperature distribution in the probe core. This ensures that heat is transferred evenly to the medium in the area of the dashed line when the probe 10 is used as a heating element. In contrast, when the probe is used as a temperature sensor, it is ensured that the thermocouple 31 is uniformly exposed to the temperature of the medium.

Fig. 4a) to 4d) show schematic cross-sections of several embodiments of a probe according to the invention, wherein the second probe sleeve has been removed for clarity. Fig. 4a) shows the embodiments shown in fig. 2a) to 2d) and fig. 3, with a support 33. Fig. 4b) shows the embodiment shown in fig. 4a), without a support. Fig. 4c) shows an embodiment in which the contact surface 14 is inclined with respect to the first longitudinal axis 15. Fig. 4d) shows an embodiment in which the contact surface 14 is perpendicular to the longitudinal axis 15. The embodiments shown in fig. 4b) and 4c) may also have a support according to the embodiment shown in fig. 4 a). The embodiments shown in fig. 4a) to 4c) enable the production of thin probes for predetermined thermocouples 31.

Fig. 5 shows a schematic front view of a thermal flow meter 40 according to the invention with a measurement tube 42, two probes 10 according to the invention arranged in the lumen of the measurement tube 42, and a housing 41 with electronic operating circuitry configured to operate the probes 10.

In order to measure the mass flow of the medium flowing through the measuring tube 40, the probe 10.1 in the medium flowing through the measuring tube 40 is heated, for example, in such a way that the temperature difference with respect to the temperature of the medium remains constant. It is suitable to measure the temperature of the medium with a second probe 10.2, which is arranged upstream of the heating probe 10.1 or, as shown in fig. 2, adjacent to the heating probe 10.1 in order to maintain the temperature difference. Assuming that the media characteristics, such as density or composition, are consistent, the mass flow rate of the media can be determined by the heating current required to maintain the temperature.

It is also possible to arrange the probes 10 one after the other in the flow direction in succession, with a first upstream probe heating the medium flowing through and a second probe located downstream together with the medium. In this case, the heating line of the first probe required for maintaining the temperature difference depends on the flow rate of the medium.

List of reference numerals

10 Probe

10.1 first Probe

10.2 second Probe

11 first probe sleeve

12 second probe sleeve

13 probe core

14 contact surface

15 first longitudinal axis

16 sub-regions

17 center of mass

21 first end

22 second end

23 third end

24 fourth end

31 thermocouple

32 solder layer/sintered layer

33 support member

34 interval of

40 flow meter

41 casing

42 measuring tube

100 method for producing a probe according to the invention

101 introducing a probe core in the form of a material to be melted into a first probe sleeve

102 melting the probe core

103 quenching the probe core to below the solidification temperature

104 exposing the probe core in the first region

105 preparing contact surfaces for attaching thermocouples

106 attach the thermocouple to the contact surface by means of a solder layer or a sintered layer

107 attaching the second probe sleeve to the first probe sleeve

Claims

1. A method for producing a probe (10) for a thermal flow meter for measuring the mass flow of a medium in a measuring tube, wherein the method has the following steps:

in a first step, a probe core (13) in the form of a material to be melted is introduced into a first probe sleeve (11), wherein the first probe sleeve (11) has an open first end (21) and a closed second end (22) remote from the first end (21);

in a second step, melting the probe core (13);

in a third step, quenching the probe core (13) to a temperature below the curing temperature;

in a fourth step, a thermocouple (31) is attached to the contact surface (14) of the cured probe core (13),

wherein the probe core (13) is exposed in a first region by partially removing a barrel wall of the first probe sleeve (11) after quenching the probe core (13),

wherein, after exposure, a second probe sleeve (12) having an open third end (23) and an open fourth end (24) is attached in a sealed manner to the first end (21) through the open third end, wherein the second probe sleeve (12) is completely wrapped around the first area.

2. The method according to claim 1, wherein the contact surface (14) is prepared by machining for attaching the thermocouple (31).

3. The method of claim 1 or 2, wherein the attaching is performed by welding.

4. The method according to claim 1 or 2, wherein the first one of the sub-regions (16) is processed such that the sub-region (16) of the probe core (13) is spaced apart from all surfaces of the first probe sleeve (11) and/or the second probe sleeve (12), wherein the sub-region (16) comprises all first cross sections of the probe core (13) which intersect or contact the contact surface (14).

5. The method according to the preceding claim 1 or 2, wherein the thermocouple (31) is attached to the contact surface (14) of the probe core (13) by means of a solder layer or a sintered layer (32).

6. A probe (10) of a thermal flow meter for measuring mass flow of a medium in a measuring tube, produced by a method according to any of the preceding claims, comprising:

a first probe sleeve (11), the first probe sleeve (11) having an open first end (21) and a closed second end (22);

a probe core (13), the probe core (13) at least partially filling the first probe sleeve (11);

a thermocouple (31), the thermocouple (31) thermally coupled to the probe core (13), wherein the thermocouple (31) is configured to increase or detect a temperature of the probe core (13);

characterized in that producing the probe core (13) comprises melting a material to be melted in the first probe sleeve (11).

7. The probe (10) according to claim 6, wherein the probe core (13) has a first longitudinal axis, an outer surface connected to the first probe sleeve (11), a centroid, and a contact surface (14) facing away from the second end (22) of the probe core (13) relative to the centroid, wherein the thermocouple (31) is attached to the contact surface (14) by a layer of solder or sintered layer (32).

8. The probe (10) according to claim 6 or 7, wherein the probe core (13) comprises a first region protruding in an axial direction from the first probe sleeve (11), wherein the first region has the contact surface (14).

9. The probe (10) according to claim 8, wherein the first region is surrounded by a second probe sleeve (12) having an open third end (23) and an open fourth end (24), the second probe sleeve (12) being connected in a sealing manner to the open first end of the first probe sleeve (11) via the third end (23), wherein the first region in sub-regions is processed such that the sub-region (16) of the probe core (13) is spaced apart from all surfaces of the first probe sleeve (11) and/or the second probe sleeve (12), wherein the sub-region comprises all first cross-sections of the probe core (13), which intersect with the contact surface (14) or comprise the contact surface (14).

10. The probe (10) according to claim 9, wherein the connection is performed by soldering.

11. The probe (10) according to claim 6, wherein the first probe sleeve (11) and/or the second probe sleeve (12) has a cylindrical design.

12. The probe (10) according to claim 11, wherein the first probe sleeve (11) and/or the second probe sleeve (12) have a rotationally symmetrical design.

13. The probe (10) according to claim 6, wherein the first probe sleeve (11) comprises stainless steel, and wherein the probe core (13) has a thermal conductivity greater than 100W/(m K), wherein the probe core has at least one metal from the list of: copper, silver, aluminum, nickel, indium, gold, tin.

14. A thermal flow meter for measuring mass flow of a medium in a measuring tube, the thermal flow meter having at least one probe (10) according to any of the preceding claims 6 to 13, wherein the thermal flow meter comprises:

a measurement tube having a second longitudinal axis; wherein the at least one probe (10) is admitted into the measurement tube;

an electronic operating circuit configured to operate the at least one probe (10).

15. The flow meter according to claim 14, wherein the thermal flow meter comprises at least two probes (10), wherein the electronically operated circuitry is configured to heat at least one first probe (10.1), wherein the electronically operated circuitry is configured to determine the temperature of the medium by means of at least one second probe (10.2).